Aggressive multi-modality therapy for oral cavity and oropharyngeal cancer have improved local control and survival; however, improved outcomes are often at the expense of significant acute and late treatment effects. A common but under-identified late effect in this population is lymphedema and fibrosis (LEF). LEF may involve both external (e.g., face) and internal structures (e.g., tongue). LEF severity is associated with substantial symptom burden, functional impairments, and decreased quality of life. However, measurement of LEF in oral cavity and oropharyngeal cancer patients is challenging. Currently, no psychometrically validated patient- reported outcome measure is available to evaluate LEF in this population. Our recent publication indicated that available clinician-reported outcome measures for external head and neck LEF are problematic. The Patterson Scale has been used in few studies to evaluate internal swelling as no current standard measure of internal LEF has been developed. However, the Patterson Scale fails to capture important anatomical sites (e.g., oral tongue) that may develop internal LEF. In addition, commonly used imaging techniques (CT scan and ultrasonography) may provide objective signals to visualize LEF-related soft tissues changes in the oral and craniofacial structures. However, these frequently used imaging modalities have not been systematically evaluated for possible use in assessing LEF in this population. The National Institute of Dental and Craniofacial Research (NIDCR) Strategic Plan 2009-2013, Objective III-1, states: Conduct well-designed, definitive clinical research studies that improve oral, dental, and craniofacial health and support more effective care delivery and health policies. The NIDCR emphasizes the need to develop new approaches to meet this objective. In keeping with the NIDCR Strategic Plan, we developed a patient-reported outcome measure and a clinician- reported outcome measure for head and neck LEF in our pilot studies. The primary goal of this study is to establish a valid, clinically useful measurement battery for head and neck LEF. Specific Aims are to: 1) determine the reliability and validity of the patient-reported outcome measure (LSIDS-H&N) for assessing LEF- related symptoms; 2) determine the reliability and validity of the clinician-reported outcome measures (HN- LEF Grading Criteria and Modified Patterson Scale) for assessing external and internal LEF; and 3) determine the reliability and validity of imaging techniques (CT scan and ultrasound with grayscale and strain elastography) in identifying site-specific LEF in oral cavity and oropharyngeal cancer patients across the trajectory of treatment, recovery, and survival. We plan to recruit 120 participants via a four-year, longitudinal study. Data collection will take place at pre-treatment, end of treatment and every 3-months up to 12-months post cancer treatment. If our aims are achieved, clinicians will be able to use the validated measures to: 1) identify LEF associated symptoms; 2) refer appropriate patients for LEF treatment; and 3) monitor the results of therapy. Researchers will be provided with much needed tools for future investigations in this area.